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A Tennessee professor is building tech that detects floods, with rural communities like Waverly in mind

William DeShazer
Debris litters Trace Creek in Waverly, Tenn., in October 2021, over 2 months after the deadly flood.

Extreme rainfall events, and the dangerous floods that follow them, are happening more often in Tennessee. This risk grows as the climate warms.

To respond to this risk, climate scientists, engineers and emergency managers rely on environmental data — data that is scarce in Tennessee. For instance, the state largely lacks, outside of rivers near urban centers, flood sensors.

“Rural areas is where we don’t have any eyes on the ground,” said Alfred Kalyanapu, an engineering professor at Tennessee Technological University.

The problem is similar to Tennessee’s absence of a mesonet, a system of sensors that track environmental conditions like soil moisture and barometric pressure in real time. At least 35 states now have mesonets, which scientists say improve extreme weather forecasts.

In 2017, Kalyanapu decided to look into flood-specific sensors, which can compliment mesonet data. He worked with students to create a low-cost solution to what he discovered is a significant infrastructure scarcity, which is often ascribed by state leaders as a funding challenge. He gathered initial support for the project through a U.S. Geological Survey grant.

His team built ultrasonic devices that sit vertically above a body of water. Each device sends soundwaves down at a 42 kilohertz frequency and records how long it takes for the echo of the sound to reflect back. This provides an accurate measurement between the sensor and the water, and it can be recorded in 15-minute intervals.

If the data points start rising, there’s probably a flood. Most of the time, these graphs will appear boring.

But the data can help us better respond to and prepare for inevitable disasters, Kalyanapu said. It can cut down the time between official warnings and danger, allow scientists to recreate a flood event in models, and help emergency managers understand the risks.

“You cannot just blindly say, ‘Hey, I have a sixth sense that tells me that’s going to flood,’ ” Kalyanapu said. “You need data to inform your decisions.”

These flood sensors cost about $500, Kalyanapu said, whereas a commercial equivalent usually costs about $20,000. To test their accuracy, Kalyanapu placed one of his sensors next to an official USGS gauge.

“Preliminary data shows it’s as good as commercial sensors, especially considering the cost,” Kalyanapu said.

Any community can reach out to the university to request a sensor. The town of Waverly, which experienced Tennessee’s second-deadliest flood event to date, had two installed.

Caroline Eggers covers environmental issues with a focus on equity for WPLN News through Report for America, a national service program that supports journalists in local newsrooms across the country. Before joining the station, she spent several years covering water quality issues, biodiversity, climate change and Mammoth Cave National Park for newsrooms in the South. Her reporting on homelessness and a runoff-related “fish kill” for the Bowling Green Daily News earned her 2020 Kentucky Press Association awards in the general news and extended coverage categories, respectively. Beyond deadlines, she is frequently dancing, playing piano and photographing wildlife and her poodle, Princess. She graduated from Emory University with majors in journalism and creative writing.
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